Piston rod for oil-less air compressor

ABSTRACT

A piston rod for oil-less air compressor mainly includes a piston head having a centered fixing hole and a plurality of through holes spaced around the fixing hole, and a disk-like check valve screwed to the fixing hole of the piston head without leaving any recess or gap between the check valve and the piston head. When the piston rod is in an upward compress stroke, the check valve tightly bears against the piston head to fully close the through holes on the piston head and keeps the piston head in a completely plane surface without any recess or gaps to form any residual air pressure there at; and when the piston rod is in a downward return stroke, the check valve is in a floating position to open the through holes on the piston head for air to enter into an air cylinder for compression later.

FIELD OF THE INVENTION

The present invention relates to a piston rod for oil-less air compressor, and more particularly to a piston rod that smoothly opens or closes an air cylinder in the air compressor and prevents forming of any residual air pressure at a piston head of the piston rod.

BACKGROUND OF THE INVENTION

FIGS. 1 and 2 shows a conventional oil-less air compressor, which includes a motor 11, an idler 12 and a bearing 13 transmitting kinetic energy produced by the motor 11 to a piston rod 14 for the latter to move in a crankcase 15 in rotary motion and a piston head 16 of the piston rod 14 to reciprocatingly move in an air cylinder 17, and a check valve 18 provided at an air outlet 21 of the air cylinder 17. When the piston head 16 is in a downward return stroke, external air is admitted into the crankcase 15 via an air inlet 19 thereof and enters into the air cylinder 17 via the piston head 16. And, when the piston head 16 is in an upward compress stroke, air in the air cylinder 17 is compressed to pass the check valve 18 and be discharged from the air outlet 21 into an externally connected air tank for storage.

The piston head 16 of the piston rod 14 is provided at a top with a long recess 161, in which a centered fixing hole 162 and two through hole 163 at two opposite sides of the fixing hole 162 are formed, and a check valve 22 is screwed to the fixing hole 162. The check valve 22 is an elongate metal plate, which is prevented from moving laterally and failing to close the through holes 163 after being locked in the long recess 161. Whereby when the piston head 16 is in an upward compress stroke, the check valve 22 tightly bears against the through holes 163 to close the same, preventing air in the air cylinder 17 from leaking via the check valve 22; and when the piston head 16 is in a downward return stroke, the check valve 22 separates from the through holes 163 to open the same, allowing air to pass therethrough into the air cylinder 17.

Since the check valve 22 is located in the long recess 161 on the piston head 16, when the piston head 16 is moved upward to compress air in the air cylinder 17, residual air pressure is formed in a gap between the check valve 22 and the long recess 161 to adversely affect the movement of air into and out of the air cylinder 17.

SUMMARY OF THE INVENTION

A primary object of the present invention is to provide an improved piston rod for oil-less air compressor, so that air could be admitted into the air compressor smoothly and no residual air pressure would form at the piston head to adversely affect the movement of air into and out of the air compressor.

To achieve the above and other objects, the piston rod for oil-less air compressor according to the present invention mainly includes a piston head having a centered fixing hole and a plurality of through holes spaced around the fixing hole directly formed on a completely plane top surface of the piston head, and a disk-like check valve screwed to the fixing hole of the piston head without leaving any recess or gap between the check valve and the piston head. When the piston rod is in an upward compress stroke, the check valve tightly bears against the piston head to fully close the through holes on the piston head and keeps the piston head in a completely plane surface without any recess or gap to form any residual air pressure thereat; and when the piston rod is in a downward return stroke, the check valve is in a floating position to open the through holes on the piston head for air to enter into an air cylinder for compression later. Therefore, the through holes on the piston head form the main air inlets to the air cylinder, and no residual air pressure would form at the completely plane top surface of the piston head.

BRIEF DESCRIPTION OF THE DRAWINGS

The structure and the technical means adopted by the present invention to achieve the above and other objects can be best understood by referring to the following detailed description of the preferred embodiments and the accompanying drawings, wherein

FIG. 1 is an assembled sectional view showing a conventional piston rod in an air compressor;

FIG. 2 is an enlarged exploded perspective view of the conventional piston rod of FIG. 1;

FIG. 3 is an enlarged exploded perspective view of a piston rod for oil-less air compressor according to the present invention;

FIG. 4 is an assembled sectional view showing the piston rod of the present invention mounted in an oil-less air compressor; and

FIG. 5 shows movements of the piston rod of the present invention in the air compressor.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Please refer to FIGS. 3 and 4 at the same time. A piston rod 14 of the present invention is mounted in an oil-less air compressor mainly having a motor 11, an idler 12, and a bearing 13. The piston rod 14 is moved in a crankcase 15 in rotary motion, such that when a piston head 16 of the piston rod 14 is in a downward return stroke, external air is admitted into the crankcase 15 via an air inlet 19 thereof, and then enters an air cylinder 17 via the piston head 16; and when the piston head 16 is in an upward compress stroke, air in the air cylinder 17 is compressed to pass through a check valve 18 and be discharged via an air outlet 21 of the air cylinder 17 into an externally connected air tank (not shown) for storage.

The piston head 16 of the piston rod 14 of the present invention has a completely plane top surface, on which a centered fixing hole 164 is provided for a check valve 23 to mount thereto, and a plurality of through holes 165 are spaced around the fixing hole 164. The check valve 23 is in the form of a round disk and has a centered through hole 231, via which a screw 232 is extended to loosely lock the check valve 23 to the fixing hole 164 on the piston head 16. After the check valve 23 is locked to the piston head 16, the top surface of the piston head 16 is kept in a completely plane surface without any recess or gap between the check valve 23 and the piston head 16. When the piston head 16 is in an upward compress stroke, air in the air cylinder 17 is compressed to pass through the check valve 18 and be discharged via the air outlet 21 of the air cylinder 17. In the process of compression, the check valve 23 tightly bears against the through holes 165 on the piston head 16 to close the same, and keeps the top surface of the piston head 16 in a completely plane surface without forming any recess or gap thereat, and thereby prevents any residual air pressure from forming at the piston head 16. Therefore, the air is compressed smoothly. And, when the piston head 16 is in the downward return stroke, air admitted into the crankcase 15 upward pushes the check valve 23 via the through holes 165, so that the check valve 23 is in an opened state for air to pass therethrough.

Please refer to FIG. 5. When the piston head 16 of the present invention is in the downward return stroke, the screw 232 of the check valve 23 is in a loose state, allowing the check valve 23 to be pushed by the entered air to an upward floating and opened position to open the through holes 165 on the piston head 16 for air to pass therethrough.

In brief, the piston rod for oil-less air compressor according to the present invention is provided at the piston head with a disk-like check valve, which keeps the piston head in a completely plane surface to prevent any residual air pressure from forming at the piston head. 

1. A piston rod for oil-less air compressor, comprising a lower end connected to a motor of said oil-less air compressor, and an upper piston head reciprocatingly moved in an air cylinder of said air compressor, so that air is admitted into said air compressor, compressed, and discharged into an externally connected air tank for storage; said piston rod being characterized in that said piston head has a completely plane top surface, on which a centered fixing hole and a plurality of through holes spaced around said fixing hole are provided, and that a disk-like check valve having a centered through hole is loosely mounted to said piston head by extending a screw through said centered through hole of said check valve into said centered fixing hole of said piston head; whereby when said piston head is in an upward compress stroke or a downward return stroke, said check valve tightly bears against said piston head to close said through holes on said piston head or is in a floating position to open said through holes on said piston head, respectively, to facilitate compression of air in said air cylinder and prevent forming of any residual air pressure at said piston head. 